This specification relates to use of free space set aside in hierarchical data documents, such as multimedia documents containing video and audio data.
The Internet is widely used to distribute multimedia information, including video and audio data. For example, content delivery networks use the Internet to deliver content to end users. A content delivery network (CDN) is a system of networked computers that cooperate to deliver multimedia documents using the Internet in a manner that can improve performance, scalability, and cost efficiency. The multimedia documents delivered can use various formats, such as MP4 (MPEG-4, Moving Picture Experts Group-4). MP4 documents can conform to the ISO/IEC (International Organization for Standardization/International Electrotechnical Commission) 14496-12:2005(E) standard.
When a multimedia document needs to be updated with new data, sometimes the document includes set aside free space, which can receive the data. Other times, the document is rewritten to accommodate the data. For example, when an editing tool needs to add new multimedia content to an MP4 document, the ‘moov’ box (or atom) is rewritten for the new document.